ApoE KO Research Articles

Vaccination targeting senescence-associated transmembrane protein alleviated cardiovascular pathology in the mice

Abstract Introduction Accumulation of senescent cells is observed in various organs including vasculature, heart and white adipose tissue with age, and known to become a substrate of pathophysiology of various cardiovascular-metabolic diseases. We have previously developed a vaccine to eliminate senescent cells, so-called "senolytic vaccine" by targeting Glycoprotein Nonmetastatic Melanoma Protein B (GPNMB) as a cellular-senescence-associated cell surface protein. We have demonstrated that GPNMB senolytic vaccine could remove senescent cells and alleviate the pathology cardiovascular-metabolic diseases. Senescence-associated adhesion molecule 1 (SAAM-1) is also known as a cell-surface membrane to increase its expression during cellular senescence in endothelial cells as well as the development of cardiovascular diseases. Here, we identified SAAM-1 as another senescence antigen and created a vaccine to eliminate senescent cells by targeting SAAM-1. Purpose This study was purposed to evaluate the efficacy of SAAM-1 vaccine for the treatment of cardiovascular diseases in mice models. Methods As a pressure overload-induced heart failure (HF) model, C57BL/6N wild type (WT) mice were underwent transverse aortic constriction (TAC) or sham opretaion at 13 weeks of age. SAAM-1 or control vaccination were given at 8 and 10 weeks of age before operation. Echocardiography examination was conducted two weeks after TAC operation, followed by tissue sampling 3 weeks after the examination. As an atherosclerosis model, ApoE KO mice were subjected to a high-fat diet (HFD) starting at 4 weeks of age. Vaccination of ApoE KO mice was administered at 8 weeks of age with SAAM-1-vaccine or control-vaccine, followed by sacrifice 4 weeks later for further analysis. ApoE-KO mice were also crossed with p16-mediated Luciferase expressing mice (p16-Luc mice) and subjected to generation of atherosclerosis model. Results SAAM-1 expression was significantly increased in left ventricle (LV) in TAC mice but its increase was suppressed by SAAM-1 vaccination. Interestingly, both worsening systolic function and dilatation of LV by pressure overload were significantly alleviated by SAAM-1 vaccination. Furthermore, expression level of senescent markers including p16 and p21, as well as several inflammation markers were increased in failing heart along with development of cardiac fibrosis, but SAAM-1 vaccine could significantly attenuate this pathological change. In ApoE KO mice, SAAM-1 vaccine decreased expression level of several inflammation markers in the mice, along with a decreasing p16 signal in the aorta. Conclusions Targeting SAAM-1 for vaccination would be a novel and promising approach to alleviating age-related cardiovascular disease.

Telomere stabilization by metformin mitigates the progression of atherosclerosis via the AMPK-dependent p-PGC-1α pathway.

Telomere dysfunction is a well-known molecular trigger of senescence and has been associated with various age-related diseases, including atherosclerosis. However, the mechanisms involved have not yet been elucidated, and the extent to which telomeres contribute to atherosclerosis is unknown. Therefore, we investigated the mechanism of metformin-induced telomere stabilization and the ability of metformin to inhibit vascular smooth muscle cell (VSMC) senescence caused by advanced atherosclerosis. The present study revealed that metformin inhibited the phenotypes of atherosclerosis and senescence in VSMCs. Metformin increased the phosphorylation of AMPK-dependent PGC-1α and thus increased telomerase activity and the protein level of TERT in OA-treated VSMCs. Mechanistically, the phosphorylation of AMPK and PGC-1α by metformin not only enhanced telomere function but also increased the protein level of TERT, whereas TERT knockdown accelerated the development of atherosclerosis and senescent phenotypes in OA-treated VSMCs regardless of metformin treatment. Furthermore, the in vivo results showed that metformin attenuated the formation of atherosclerotic plaque markers in the aortas of HFD-fed ApoE KO mice. Although metformin did not reduce plaque size, it inhibited the phosphorylation of the AMPK/PGC-1α/TERT signaling cascade, which is associated with the maintenance and progression of plaque formation, in HFD-fed ApoE KO mice. Accordingly, metformin inhibited atherosclerosis-associated phenotypes in vitro and in vivo. These observations show that the enhancement of telomere function by metformin is involved in specific signaling pathways during the progression of atherosclerosis. These findings suggest that telomere stabilization by metformin via the AMPK/p-PGC-1α pathway might provide a strategy for developing therapeutics against vascular diseases such as atherosclerosis.

Quercetin Attenuates KLF4-Mediated Phenotypic Switch of VSMCs to Macrophage-like Cells in Atherosclerosis: A Critical Role for the JAK2/STAT3 Pathway.

The objective of this study was to elucidate the protective role of quercetin in atherosclerosis by examining its effect on the phenotypic switch of vascular smooth muscle cells (VSMCs) to macrophage-like cells and the underlying regulatory pathways. Aorta tissues from apolipoprotein E-deficient (ApoE KO) mice fed a high-fat diet (HFD), treated with or without 100 mg/kg/day quercetin, were analyzed for histopathological changes and molecular mechanisms. Quercetin was found to decrease the size of atherosclerotic lesions and mitigate lipid accumulation induced by HFD. Fluorescence co-localization analysis revealed a higher presence of macrophage-like vascular smooth muscle cells (VSMCs) co-localizing with phospho-Janus kinase 2 (p-JAK2), phospho-signal transducer and activator of transcription 3 (p-STAT3), and Krüppel-like factor 4 (KLF4) in regions of foam cell aggregation within aortic plaques. However, this co-localization was reduced following treatment with quercetin. Quercetin treatment effectively inhibited the KLF4-mediated phenotypic switch in oxidized low-density lipoprotein (ox-LDL)-loaded mouse aortic vascular smooth muscle cells (MOVAS), as indicated by decreased expressions of KLF4, LGALS3, CD68, and F4/80, increased expression of alpha smooth muscle actin (α-SMA), reduced intracellular fluorescence Dil-ox-LDL uptake, and decreased lipid accumulation. In contrast, APTO-253, a KLF4 activator, was found to reverse the effects of quercetin. Furthermore, AG490, a JAK2 inhibitor, effectively counteracted the ox-LDL-induced JAK2/STAT3 pathway-dependent switch to a macrophage-like phenotype and lipid accumulation in MOVAS cells. These effects were significantly mitigated by quercetin but exacerbated by coumermycin A1, a JAK2 activator. Our research illustrates that quercetin inhibits the KLF4-mediated phenotypic switch of VSMCs to macrophage-like cells and reduces atherosclerosis by suppressing the JAK2/STAT3 pathway.

20( S )-Protopanaxatriol Improves Atherosclerosis by Inhibiting Low-Density Lipoprotein Receptor Degradation in ApoE KO Mice.

Atherosclerosis (AS) is a chronic progressive disease caused by various factors and causes various cerebrovascular and cardiovascular diseases (CVDs). Reducing the plasma levels of low-density lipoprotein cholesterol is the primary goal in preventing and treating AS. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in regulating low-density lipoprotein cholesterol metabolism. Panax notoginseng has potent lipid-reducing effects and protects against CVDs, and its saponins induce vascular dilatation, inhibit thrombus formation, and are used in treating CVDs. However, the anti-AS effect of the secondary metabolite, 20( S )-protopanaxatriol (20( S )-PPT), remains unclear. In this study, the anti-AS effect and molecular mechanism of 20( S )-PPT were investigated in vivo and in vitro by Western blotting, real-time polymerase chain reaction, enzyme-linked immunosorbent assay, immunofluorescence staining, and other assays. The in vitro experiments revealed that 20( S )-PPT reduced the levels of PCSK9 in the supernatant of HepG2 cells, upregulated low-density lipoprotein receptor protein levels, promoted low-density lipoprotein uptake by HepG2 cells, and reduced PCSK9 mRNA transcription by upregulating the levels of forkhead box O3 protein and mRNA and decreasing the levels of HNF1α and SREBP2 protein and mRNA. The in vivo experiments revealed that 20( S )-PPT upregulated aortic α-smooth muscle actin expression, increased the stability of atherosclerotic plaques, and reduced aortic plaque formation induced by a high-cholesterol diet in ApoE -/- mice (high-cholesterol diet-fed group). Additionally, 20( S )-PPT reduced the aortic expression of CD68, reduced inflammation in the aortic root, and alleviated the hepatic lesions in the high-cholesterol diet-fed group. The study revealed that 20( S )-PPT inhibited low-density lipoprotein receptor degradation via PCSK9 to alleviate AS.

Therapy Combining Glucagon-Like Peptide-1 Receptor Agonist with Sodium-Glucose Cotransporter 2 Inhibitor Suppresses Atherosclerosis in Diabetic ApoE-Deficient Mice.

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) and sodium-glucose cotransporter 2 inhibitors (SGLT2i) have beneficial effects on cardiovascular disease in addition to their glucose-lowering effects. In this study, the effects of these drugs, when used individually or in combination, on cardiovascular atherosclerotic lesion development were compared in diabetic ApoE-deficient (ApoE KO) hyperlipidemic mice. ApoE-KO mice were treated with streptozotocin and nicotinamide, generating a type 2 diabetes model. The mice were randomly divided into four groups: vehicle-treated (untreated), liraglutide (LIRA), ipragliflozin (IPRA), and combination therapy (combo). These mice, as well as non-diabetic controls, were fed a high-fat diet. After 8 weeks of drug administration, the heart and aorta were removed and analyzed. Atherosclerotic lesions evaluated by oil red O (ORO) staining were significantly larger in the untreated group (13.4±0.8% of the total aortic area) than in the non-diabetic controls (4.4±0.5%, p<0.01), while being reduced in the combo group (6.0±1.0%, p<0.01) as compared with the untreated group. The ORO stain-positive area in the LIRA and IPRA groups tended to be reduced but their differences were not statistically significant. Transcript levels of Mcp1 and Sirt1 were significantly reduced and increased, respectively, in the combo compared with the untreated group, while no significant changes were observed in the monotherapy groups. The data suggest that combination therapy with liraglutide and ipragliflozin may be an efficient regimen for preventing the development of atherosclerosis in diabetic mice deficient in ApoE.

Repeated Injection of Very Small Superparamagnetic Iron Oxide Particles (VSOPs) in Murine Atherosclerosis: A Safety Study.

Citrate-coated electrostatically stabilized very small superparamagnetic iron oxide particles (VSOPs) have been successfully tested as magnetic resonance angiography (MRA) contrast agents and are promising tools for molecular imaging of atherosclerosis. Their repeated use in the background of pre-existing hyperlipidemia and atherosclerosis has not yet been studied. This study aimed to investigate the effect of multiple intravenous injections of VSOPs in atherosclerotic mice. Taurine-formulated VSOPs (VSOP-T) were repeatedly intravenously injected at 100 µmol Fe/kg in apolipoprotein E-deficient (ApoE KO) mice with diet-induced atherosclerosis. Angiographic imaging was carried out by in vivo MRI. Magnetic particle spectrometry was used to detect tissue VSOP content, and tissue iron content was quantified photometrically. Pathological changes in organs, atherosclerotic plaque development, and expression of hepatic iron-related proteins were evaluated. VSOP-T enabled the angiographic imaging of heart and blood vessels with a blood half-life of one hour. Repeated intravenous injection led to VSOP deposition and iron accumulation in the liver and spleen without affecting liver and spleen pathology, expression of hepatic iron metabolism proteins, serum lipids, or atherosclerotic lesion formation. Repeated injections of VSOP-T doses sufficient for MRA analyses had no significant effects on plaque burden, steatohepatitis, and iron homeostasis in atherosclerotic mice. These findings underscore the safety of VSOP-T and support its further development as a contrast agent and molecular imaging tool.

Aster glehni Extract, Including Caffeoylquinic Acids as the Main Constituents, Induces PPAR β/δ-Dependent Muscle-Type Change and Myogenesis in Apolipoprotein E Knockout Mice.

To probe the functions of Aster glehni (AG) extract containing various caffeoylquinic acids on dyslipidemia, obesity, and skeletal muscle-related diseases focused on the roles of skeletal muscle, we measured the levels of biomarkers involved in oxidative phosphorylation and type change of skeletal muscle in C2C12 cells and skeletal muscle tissues from apolipoprotein E knockout (ApoE KO) mice. After AG extract treatment in cell and animal experiments, western blotting, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) were used to estimate the levels of proteins that participated in skeletal muscle type change and oxidative phosphorylation. AG extract elevated protein expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), phosphorylated 5'-AMP-activated protein kinase (p-AMPK), peroxisome proliferator-activated receptor beta/delta (PPARβ/δ), myoblast determination protein 1 (MyoD), and myoglobin in skeletal muscle tissues. Furthermore, it elevated the ATP concentration. However, protein expression of myostatin was decreased by AG treatment. In C2C12 cells, increments of MyoD, myoglobin, myosin, ATP-producing pathway, and differentiation degree by AG were dependent on PPARβ/δ and caffeoylquinic acids. AG extract can contribute to the amelioration of skeletal muscle inactivity and sarcopenia through myogenesis in skeletal muscle tissues from ApoE KO mice, and function of AG extract may be dependent on PPARβ/δ, and the main functional constituents of AG are trans-5-O-caffeoylquinic acid and 3,5-O-dicaffeoylquinic acid. In addition, in skeletal muscle, AG has potent efficacies against dyslipidemia and obesity through the increase of the type 1 muscle fiber content to produce more ATP by oxidative phosphorylation in skeletal muscle tissues from ApoE KO mice.

IL-33 Reduces Saturated Fatty Acid Accumulation in Mouse Atherosclerotic Foci.

The cellular and molecular mechanisms of atherosclerosis are still unclear. Type 2 innate lymphocytes (ILC2) exhibit anti-inflammatory properties and protect against atherosclerosis. This study aimed to elucidate the pathogenesis of atherosclerosis development using atherosclerosis model mice (ApoE KO mice) and mice deficient in IL-33 receptor ST2 (ApoEST2 DKO mice). Sixteen-week-old male ApoE KO and ApoEST2 DKO mice were subjected to an 8-week regimen of a high-fat, high-sucrose diet. Atherosclerotic foci were assessed histologically at the aortic valve ring. Chronic inflammation was assessed using flow cytometry and real-time polymerase chain reaction. In addition, saturated fatty acids (palmitic acid) and IL-33 were administered to human aortic endothelial cells (HAECs) to assess fatty acid metabolism. ApoEST2 DKO mice with attenuated ILC2 had significantly worse atherosclerosis than ApoE KO mice. The levels of saturated fatty acids, including palmitic acid, were significantly elevated in the arteries and serum of ApoEST2 DKO mice. Furthermore, on treating HAECs with saturated fatty acids with or without IL-33, the Oil Red O staining area significantly decreased in the IL-33-treated group compared to that in the non-treated group. IL-33 potentially prevented the accumulation of saturated fatty acids within atherosclerotic foci.

Nalmefene, an opioid receptor modulator, aggravates atherosclerotic plaque formation in apolipoprotein E knockout mice by enhancing oxidized low-density lipoprotein uptake in macrophages

Nalmefene, an antagonist of mu- and delta-opioid receptors and a partial agonist of kappa-opioid receptors, has shown promise in reducing alcohol consumption among patients with alcohol dependence. Opioid receptors play pivotal roles in various physiological processes, including those related to peripheral inflammatory diseases such as colitis and arthritis, as well as functions in the immune system and phagocytosis. Atherosclerosis, a chronic inflammatory disease, progresses through the phagocytosis and uptake of oxidized low-density lipoprotein (oxLDL) by macrophages in atherosclerotic plaques. Despite this knowledge, it remains unclear whether nalmefene influences the formation of atherosclerotic plaques and increases the risk of serious cardiovascular events. This study aims to elucidate the impact of nalmefene on atherosclerosis in apolipoprotein E knockout (ApoE KO) mice and peritoneal macrophages in vitro.In this experiment, 8-week-old male ApoE KO mice were fed a high-fat diet intraperitoneally administered either vehicle (saline) or nalmefene (1 mg and 3 mg kg−1 day−1) for 21 days. Oil red O-staining and immunohistochemistry with an anti-MOMA2 (monocyte/macrophage) antibody showed that a dose-dependent increase in atherosclerotic plaque formation and augmentation of macrophage-rich plaque formation in ApoE-KO mice. Further investigations focused on the effects of nalmefene on the expression of scavenger receptor CD36 in RAW264.7 cells, conducted through western blotting analysis. Nalmefene demonstrated a significant increase in CD36 protein expression in RAW264.7 cells. To explore the impact on oxidized LDL uptake in peritoneal macrophages, cells were treated with nalmefene (300 μg/mL) for 24 h, followed by the addition of DiI-labeled oxLDL (DiI-oxLDL) for 4 h. Nalmefene significantly enhanced DiI-oxLDL uptake in macrophages. Additionally, treatment with nalmefene (300 μg/mL) for 24 h decreased the mRNA expression of mu-, delta-, and kappa-opioid receptors in RAW264.7 cells.In conclusion, nalmefene may augment oxLDL uptake by macrophages through increased CD36 expression and decreased opioid receptor, thereby contributing to atherosclerotic plaque formation and vulnerability. Consequently, the use of nalmefene may be associated with an elevated risk of cardiovascular events.

Protective effects of imeglimin on the development of atherosclerosis in ApoE KO mice treated with STZ

BackgroundImeglimin is a new anti-diabetic drug which promotes insulin secretion from pancreatic β-cells and reduces insulin resistance in insulin target tissues. However, there have been no reports examining the possible anti-atherosclerotic effects of imeglimin. In this study, we investigated the possible anti-atherosclerotic effects of imeglimin using atherosclerosis model ApoE KO mice treated with streptozotocin (STZ).MethodsApoE KO mice were divided into three groups: the first group was a normoglycemic group without injecting STZ (non-DM group, n = 10). In the second group, mice were injected with STZ and treated with 0.5% carboxymethyl cellulose (CMC) (control group, n = 12). In the third group, mice were injected with STZ and treated with imeglimin (200 mg/kg, twice daily oral gavage, n = 12). We observed the mice in the three groups from 10 to 18 weeks of age. Plaque formation in aortic arch and expression levels of various vascular factors in abdominal aorta were evaluated for each group.ResultsImeglimin showed favorable effects on the development of plaque formation in the aortic arch in STZ-induced hyperglycemic ApoE KO mice which was independent of glycemic and lipid control. Migration and proliferation of vascular smooth muscle cells and infiltration of macrophage were observed in atherosclerotic lesions in STZ-induced hyperglycemic ApoE KO mice, however, which were markedly reduced by imeglimin treatment. In addition, imeglimin reduced oxidative stress, inflammation and inflammasome in hyperglycemic ApoE KO mice. Expression levels of macrophage makers were also significantly reduced by imeglimin treatment.ConclusionsImeglimin exerts favorable effects on the development of plaque formation and progression of atherosclerosis.

MSC exosomes attenuate sterile inflammation and necroptosis associated with TAK1-pJNK-NFKB mediated cardiomyopathy in diabetic ApoE KO mice.

Diabetes is a debilitating disease that leads to complications like cardiac dysfunction and heart failure. In this study, we investigated the pathophysiology of diabetes-induced cardiac dysfunction in mice with dyslipidemia. We hypothesize diabetes in ApoE knockout (ApoE-/-) mice induces cardiac dysfunction by increasing inflammation and necroptosis. ApoE-/- mice were divided into experimental groups: Control, Streptozotocin (STZ), STZ + MSC-Exo (mesenchymal stem cell-derived exosomes), and STZ+MEF-Exo (Mouse embryonic fibroblast derived exosomes). At Day 42, we assessed cardiac function, collected blood and heart tissues. Heart tissue samples were analyzed for inflammation, necroptosis, signaling mechanism, hypertrophy and adverse structural remodeling using histology, immunohistochemistry, western blotting, RT-PCR, cytokine array and TF array. STZ treated ApoE-/- mice developed diabetes, with significantly (p<0.05) increased blood glucose and body weight loss. These mice developed cardiac dysfunction with significantly (p<0.05) increased left ventricular internal diameter end diastole and end systole, and decreased ejection fraction, and fractional shortening. We found significant (p<0.05) increased expression of inflammatory cytokines TNF- a, IL-6, IL-1a, IL-33 and decreased IL-10 expression. Diabetic mice also exhibited significantly (p<0.05) increased necroptosis marker expression and infiltration of inflammatory monocytes and macrophages. MSC-Exos treated mice showed recovery of diabetes associated pathologies with significantly reduced blood glucose, recovered body weight, increased IL-10 secretion and M2 polarized macrophages in the heart. These mice showed reduced TAK1-pJNK-NFKB inflammation associated expression and improved cardiac function with significantly reduced cardiac hypertrophy and fibrosis compared to diabetic mice. Treatment with MEF-Exos did not play a significant role in attenuating diabetes-induced cardiomyopathy as these treatment mice presented with cardiac dysfunction and underlying pathologies observed in STZ mice. Thus, we conclude that cardiac dysfunction develops in diabetic ApoE-/- mice, arising from inflammation, necroptosis, and adverse tissue remodeling, which is ameliorated by MSC-Exos, a potential therapeutic for diabetes-induced cardiomyopathy.

Gastrodin Suppresses the Progression of Atherosclerosis and Vascular Inflammation by Regulating TLR4/NF-κB Pathway.

Elevated levels of plasma triglycerides (TG) and cholesterol have been shown to contribute to the pathogenesis of several cardiovascular risk factors, such as atherosclerosis, a primary cause of mortality. Gastrodin (Gas) is an effective polyphenol extracted from Chinese natural herbal Gastrodiae elata Blume, which has been documented to be effective against atherosclerosis. However, the related mechanisms remain largely unclear. The current investigation elucidated the involvement of Gas in the development of AS generated by a high-fat diet in mice lacking the apolipoprotein E gene (ApoE-/-). The findings of our study indicate that the administration of Gas had a beneficial effect on hyperlipidemia in mice that were given a high-fat diet and lacked the ApoE gene. Specifically, Gas supplementation resulted in a reduction in blood levels of oxidized low-density lipoprotein (ox-LDL), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-alpha (TNF-α). Additionally, the administration of Gas resulted in the suppression of lesions in the en face aortas of ApoE KO mice, accompanied by a modest improvement in lipid profiles. The intervention demonstrated the capacity to impede the development of atherosclerotic lesions and promote characteristics associated with plaque stability. The administration of Gas prevented inflammation in the aorta by decreasing the expression of IL-6, TNF-α, and MCP-1. Additionally, Gas had a mitigating effect on TLR4/NF-κB pathway components in the aorta of ApoE-/- mice. Furthermore, it has been shown that Gas has the potential to mitigate the harm caused to human umbilical vein endothelial cells (HUVECs) by ox-LDL, perhaps via inhibiting inflammation through the TLR4/NF-κB pathway. This study shows that Gas may potentially mitigate the development of atherosclerosis via its pleiotropic effects, including improvements in lipid profiles and anti-inflammatory properties.

Visualization of Pulse-Wave Velocity on Arterial Wall of Mice Through High-Frequency Ultrafast Doppler Imaging.

Arterial pulse-wave velocity (PWV) is widely used in clinical applications to assess cardiovascular diseases. Ultrasound methods have been proposed for estimating regional PWV in human arteries. Furthermore, high-frequency ultrasound (HFUS) has been applied to perform preclinical small-animal PWV measurements; however, electrocardiogram (ECG)-gated retrospective imaging is required to achieve high-frame-rate imaging, which might be affected by arrhythmia-related problems. In this article, HFUS PWV mapping based on 40-MHz ultrafast HFUS imaging is proposed to visualize PWV on mouse carotid artery to measure arterial stiffness without ECG gating. In contrast to most other studies that used cross-correlation methods to detect arterial motion, ultrafast Doppler imaging was applied in this study to measure arterial wall velocity for PWV estimations. The performance of the proposed HFUS PWV mapping method was verified using a polyvinyl alcohol (PVA) phantom with various freeze-thaw cycles. Small-animal studies were then performed in wild-type (WT) mice and in apolipoprotein E knockout (ApoE KO) mice that were fed a high-fat diet (for 16 and 24 weeks). The Young's modulus of the PVA phantom measured through HFUS PWV mapping was 15.3 ± 0.81, 20.8 ± 0.32, and 32.2 ± 1.11 kPa for three, four, and five freeze-thaw cycles, respectively, and the corresponding measurement biases (relative to theoretical values) were 1.59%, 6.41%, and 5.73%, respectively. In the mouse study, the average PWVs were 2.0 ± 0.26, 3.3 ± 0.45, and 4.1 ± 0.22 m/s for 16-week WT, 16-week ApoE KO, and 24-week ApoE KO mice, respectively. The PWVs of ApoE KO mice increased during the high-fat diet feeding period. HFUS PWV mapping was used to visualize the regional stiffness of mouse artery, and a histology confirmed that the plaque formation in the bifurcation region increased the regional PWV. All the results indicate that the proposed HFUS PWV mapping method is a convenient tool for investigating arterial properties in preclinical small-animal studies.

Investigating the Role of APOE Genotype in Human Microglia

AbstractBackgroundAlthough the pivotal role of apolipoprotein E () in AD has been recognized for three decades, its function in different brain cells is far from understood. Knockout studies of the APOE gene may shed light of the function of ApoE. The aim of the present study was to unravel its function in induced pluripotent stem cell (iPSC) derived microglia.MethodWe studied two human iPSC‐derived microglia cell cultures, one derived from a healthy control (Bioni010‐C – endogenous genotype apolipoprotein E34 (APOE34)) and one from an AD patient (UKBi011‐A – endogenous genotype APOE44) and their edited isogenic cell‐lines (for UKBi011‐A, APOE22 and APOE33 and for Bioni010‐C, hemizygous due to gene editing, APOE2‐ and APOE3‐ (32971461, 29753274)). Additionally, APOE KO lines were generated from both backgrounds. We performed whole genome transcriptomic (IlluminaTruSequencing) and proteomic (TMT‐labelled Nano‐LC peptidomic MS) analysis (n = six per genotype). For transcriptomic data, log2‐normalized intensities were analysed with (in R); there were 13115 unique transcripts. For proteomics analysis, after global normalization, the data were locally normalized (by protein), the limma package was used to calculate FDR‐corrected p‐values (1% cut off); there were 3975 (Bioni010 samples) and 4349 (UKBi011 samples) proteins. In the quality control analysis for the proteomics, we excluded one outlier of the six per line based on principle component/Euclidean distance analysis. We extracted pairwise comparisons to APOE KO in transcriptomic (|logFC|&gt;0.5, FDR &lt;0.05) and proteomic (|logFC|&gt;0 and FDR &lt;0.05) data.ResultTwenty transcripts (including APOE) were concordantly differentially expressed across all comparisons between APOE‐expressing and KO. These are broadly involved in processes related to mitochondrial function/organization, apoptosis, transcriptional regulation, immune functions, extracellular matrix, and energy metabolism among others. Seven proteins were concordantly differentially expressed across all pairwise comparisons with APOE KO, involved in extracellular matrix, immune signalling, energy metabolism, and cytoskeletal structure.ConclusionOur study finds APOE knockout leads to a number of changes related to immune, mitochondrial, and extracellular matrix genes, suggesting that APOE in human iPSC‐derived microglia cells influences immune and mitochondrial functions.

Novel mechanisms to enhance omega‐3 brain metabolism with APOE4

AbstractBackgroundNeuroprotective nutritional interventions involving greater consumption of polyunsaturated fats (Mediterranean diet, fish consumption or DHA supplements) are less effective in APOE4 carriers with dementia compared to non‐carriers. We recently demonstrated greater activation of calcium dependent phospholipase A2 (cPLA2) in APOE4 compared with non‐APOE4 using both postmortem human brains and in brain tissues from APOE4 animal models. Activation of cPLA2 is associated with lower omega‐3 brain levels and lower measures of blood‐brain barrier (BBB) integrity as assessed using 7T DCE MRI to derive contrast transfer values (K trans).MethodHere, we present new data on aging (18 months) old APOE mouse models on a low DHA diet, APOE4‐TR mice treated with LPS and APOE knock out mice as a model of lower BBB integrity. All models were treated with the brain penetrant cPLA2 inhibitor ASB14780 at 10 mg/kg IP daily over 8 weeks in the aging model and acutely (7 days) in the younger LPS and APOE KO models.ResultcPLA2 inhibition was associated with increased brain omega‐3 levels in both the aging APOE4 model and in the younger APOE4 mice treated acutely with LPS. In the aging APOE4 mouse model, cPLA2 inhibition associated with better performance on novel object recognition, improved synaptic markers, and lower microglial activation. In the APOE KO model, treatment was associated with improved measures of BBB with lower K trans following treatment (Figure).ConclusionThe results here demonstrate how neuroinflammation associated with APOE4 depletes brain omega‐3s via activation of cPLA2 and how reducing cPLA2 activity can rescue this phenotype. The development of specific and potent brain penetrant cPLA2 inhibitors promises to enhance the brain effects of omega‐3 enriched diets by limiting the effects of neuroinflammation on the aging APOE4 brain.

The relationship between ApoE4 and lipid dysregulation in glia of the PS19 mouse model of tauopathy

AbstractBackgroundApolipoprotein E4 (apoE), the major lipoprotein in the brain, plays an essential role in brain`s lipid homeostasis; furthermore, the presence of the apoE4 allele is the strongest genetic risk factor for developing late‐onset AD compared to most common apoE3 and protective apoE2 alleles. Recent studies in iPSC microglia and astrocytes demonstrate that apoE modulates cholesterol dysfunction and inflammatory responses in an isoform‐specific fashion. However, it is not known if lipid accumulation in glia mediates toxic effects in vivo in the context of tauopathy and neurodegeneration.MethodIn this work we used the combination unbiased lipidomics coupled with immunostainings to dissect the role of apoE and apoE isoforms in glial lipid metabolism of tauopathy P301S tau transgenic mice with a targeted replacement of murine apoE with human ApoE4, ApoE3, or ApoE KO. We further treated the P301S/ApoE4 mice with the LXR agonist GW3965 to test if promoting cholesterol efflux in P301S mice would reduce tau pathology and neurodegeneration in this model.ResultsBy performing unbiased lipidomic analysis of forebrain samples, we demonstrate that P301S/ApoE KI mice accumulate significant amounts of specific cholesteryl esters, oxidized sterols and endolysosomal BMP lipids in an ApoE‐isoform and Tau‐dependent manner. We further show that microglia from aged 9.5 months old P301S/ApoE4 mice accumulate significant amounts of neutral BODIPY‐positive lipid inclusions within lysosomes. Next, we demonstrate that the oral administration of the LXR agonist GW3965 for 3 months significantly reduces p‐tau‐positive AT8 immunostaining in cortex and hippocampus, protects from associated brain neurodegeneration, and improves nesting behavior in 9.5 months old P301S/ApoE4 mice. Using bulk RNA sequencing and immunostaining, we show that LXR agonist diet induces changes in cholesterol biosynthesis and metabolism that result in a significant reduction of neuroinflammatory responses in aged P301S/ApoE4 mice. Lastly, using unbiased lipidomics of forebrain tissues we demonstrate that P301S/ApoE4 mice on LXR diet exhibit significantly lower levels of cholesterol esters when compared to tau transgenic animals on control diet.ConclusionsTogether, we demonstrate that ApoE4 promotes lipid accumulation in glia in the setting of tauopathy and that reducing the accumulation of these lipids by LXR activation is neuroprotective.

The Effect of APOE Genotype on Endolysosomal Dynamics in Neurons

AbstractBackgroundAPOE genotype is known as the most important genetic risk factor for developing AD. Understanding the cellular differences between the ApoE isoforms will be crucial for understanding the fundamental pathways that are disrupted in AD and potential pathways that can be therapeutically targeted. Accumulating evidence is suggesting that ApoE isoforms influence the endosomal system, one of the earliest sites affected in AD. However, our understanding of how the isoforms affect the endolysosomal pathway is still limited. We aim to understand how ApoE isoforms affect the endosomal pathway, but also understand the dynamics of the system in the context of ageing and activity.MethodTo study cellular changes in neurons we are using primary hippocampal/cortical brain cultures, harvested from ApoE KO mice and targeted replacement mice, expressing human ApoE3 or ApoE4. Neurons in culture have accelerated maturation and with time in culture gradually show signs of age‐like stress. To study ApoE in the context of ageing, mature cultures at 18 days in vitro (DIV18) and more aged cultures at DIV25 were used. To explore how ApoE isoforms adapt to elevated activity DIV18 primary cultures were treated for 48 H with the GABA receptor antagonist bicuculline.ResultOur preliminary data suggests that especially early endosomes are affected in ApoE4 neurons. Interestingly, the appearance of the early endosomes seems to differ depending on both the intracellular localization and time in culture. However, the protein level of the early endosomal marker EEA1 remained unaltered in ApoE4. In addition, preliminary data indicate that ApoE4 has reduced capacity to adjust the endosomal system following 48 hours bicuculline treatment. When studying the trafficking of fluorescently tagged EGF (which has an established endolysosomal route), preliminary results show potential differences between both DIV18 and DIV25 but also between ApoE‐isoforms, suggesting that both time in culture and ApoE isoforms influence endolysosomal trafficking.ConclusionThe endolysosomal pathway is a highly dynamic and important system for all cells, including neurons and is increasingly linked to AD. Our preliminary findings point toward an ApoE isoform effect on endosomal trafficking and that its dynamics might be disrupted by ApoE4.

The SGLT2I Dapagliflozin reverses metabolic stress driving myocardial inflammation in a mouse model of heart failure with preserved ejection fraction: insights from single-cell RNA sequencing

Abstract Background Heart failure with preserved ejection fraction (HFpEF) is often associated with metabolic distress and represents a therapeutic challenge. Metabolism-induced systemic inflammation links comorbidities with HFpEF. How metabolic changes impact myocardial inflammation in the context of HFpEF is not known. Methods We generated a model of metabolic HFpEF by feeding ApoE knockout (ApoE KO) mice a high-fat diet (HFD), and used single-cell expression analysis (scRNA-seq) on CD45+ cardiac cells to evaluate the involvement of inflammation. By focusing our analysis on macrophages, we obtained high-resolution identification of subsets of these cells in the heart, enabling us to study the outcomes of metabolic distress on the cardiac macrophage infiltrate and identify a macrophage-to-cardiomyocyte (CMC) regulatory axis. To test whether a clinically relevant sodium glucose cotransporter-2 inhibitor (SGLT2i) could ameliorate the cardiac immune infiltrate profile in our model, ApoE KO-HDF mice were randomized to receive the SGLT2i dapagliflozin (DAPA) or vehicle for 8 weeks. Results We describe a new metabolic HFpEF model: mice present with reduced diastolic function, reduced exercise tolerance, and increased pulmonary congestion associated with cardiac lipid overload and reduced polyunsaturated fatty acids. The main immune cell types infiltrating the heart included 4 sub-populations of resident and monocyte-derived macrophages displaying a pro-inflammatory profile exclusively in ApoE KO-HFD mice. Lipid overload had a direct effect on inflammatory gene activation in macrophages, mediated through endoplasmic-reticulum stress pathways. Investigation of the macrophage-to-CMC regulatory axis revealed the potential effects on CMCs of multiple inflammatory cytokines secreted by macrophages, impacting pathways such as hypertrophy, fibrosis, and autophagy. Finally, we describe the anti-inflammatory effect of SGLT2i. Conclusions Through a newly described model of HFpEF based on metabolic stress, and using scRNA-seq, we have determined the effects of metabolic distress on cardiac inflammatory cells, in particular on macrophages, and suggest SGLT2i as potential therapeutic agents for the targeting of a specific phenotype of HFpEF.

FRI107 Ketogenic Diet Prevents Development Of Atherosclerotic Plaques In Apolipoprotein E Knockout Mice

Abstract Disclosure: V. Marzolla: None. A. Armani: None. C. Mammi: None. S. Gorini: None. E. Camajani: None. M. Caprio: None. Higher aldosterone (aldo) levels are associated with increased risk of cardiovascular ischemic events and mortality. It has been demonstrated that aldo accelerates the development of atherosclerosis in apolipoprotein E knockout mice (ApoE KO). Ketogenic diet (KD) positively impacts several cardiovascular risk factors, yet its effect on atherosclerosis is elusive. We hypothesize that KD protects from development of atherosclerotic plaques in ApoE KO mice, a murine model of atherosclerosis. Eight-week-old male ApoE KO mice were fed a KD (90,5% Kcal from fat, 0.4% Kcal from carbohydrate, 9.1% Kcal from protein) or a moderate high fat die (HFD) (42% Kcal from fat, 42.7% Kcal from carbohydrate, 15.2% Kcal from protein) and treated with aldosterone (aldo, 6 μg/mouse per day) or vehicle through osmotic mini-pumps. Cholesterol content was comparable in KD and HFD. After 4 weeks of treatment, in all experimental groups, intraperitoneal glucose tolerance test was performed, and peripheral blood samples were collected. We analysed cryosections of embedded aortic root to quantify the atherosclerotic plaque size, lipid and collagen content. We assessed vascular inflammation in speciments of thoracic aorta by analysing pro-inflammatory (ICAM-1, VCAM-1, IL-6, TNF-α, MCP-1) and anti-inflammatory (Arg-1, RETNLA, CCL5) genes. In ApoE KO mice treated with aldo, KD determined a significant improvement in glucose tolerance, compared to mice fed a HFD, without any significant effect on body weight. Beta-hydroxybutyrate levels were always significantly higher in KD-mice than in AD-mice, confirming nutritional ketosis in KD-mice. Analysis of aortic root showed that aldo treatment determined a significant increase in atherosclerotic plaque size and lipid content in HFD-mice. Such effects were significantly reduced in KD-mice, suggesting a favorable impact of ketosis in preventing atherosclerosis development. Plaque fibrosis did not differ among treatment groups. Finally, we observed a significant reduction in vascular inflammatory markers in KD-mice, when compared to HFD-mice. In particular, KD determined a significant reduction in gene expression of pro-inflammatory markers (ICAM-1, VCAM-1, IL-6, TNF-α, MCP-1) with the concomitant up-regulation of anti-inflammatory markers (Arg-1, RETNLA, CCL5), compared to HFD. The study suggests KD as a potential non-pharmacological approach to prevent the development of atherosclerotic disease in subjects with high cardiovascular risk. Presentation: Friday, June 16, 2023

TNF-α Preconditioning Improves the Therapeutic Efficacy of Mesenchymal Stem Cells in an Experimental Model of Atherosclerosis.

Atherosclerosis (AS) is an inflammatory disease involving multiple factors in its initiation and development. In recent years, the potential application of mesenchymal stem cells (MSCs) for treating AS has been investigated. This study examined the effect of TNF-α preconditioning on MSCs' therapeutic efficacy in treating AS in ApoE KO mice. TNF-α-treated MSCs were administered to high-fat diet-treated ApoE KO mice. Cytokine and serum lipid levels were measured before and after treatment. Cryosections of the atherosclerotic aorta were stained with Oil-Red-O, and the relative areas of atherosclerotic lesions were measured. The level of Tregs were increased in TNF-α-MSC-treated animals compared to the MSCs group. In addition, the systemic administration of TNF-α-MSCs to ApoE KO mice reduced the level of proinflammatory cytokines such as TNF-α and IFN-γ and increased the level of the immunosuppressive IL-10 in the blood serum. Total cholesterol and LDL levels were decreased, and HDL levels were increased in the TNF-α-MSCs group of ApoE KO mice. A histological analysis showed that TNF-α-MSCs decreased the size of the atherosclerotic lesion in the aorta of ApoE KO mice by 38%, although there was no significant difference when compared with untreated MSCs. Thus, our data demonstrate that TNF-α-MSCs are more effective at treating AS than untreated MSCs.